Summary
Recent pointing showed systematic azimuth residuals that have now been mitigated. Nighttime inclinometry provided a new track model.

Recent pointing data have shown strong azimuth residuals :

Most simply diagnosed as due to a change in the NS orientation of the major axis, by 4", this somewhat unbelievable result was also reproducible by a 0.25^s clock error. No change was made to the 7-parameter pointing model. On 18 May NPR changed the model and the pointing appeared to improve :

although the data still suggest a clock error of 0.31^s + 0.06.

On 18 May nighttime inclinometry was done :

    Datasets        HST     mean leg temperatures   Humidity
                   start      start   middle   end       %
  ( 20010508 cw     11:20      5.6      7.0     8.0     30 )  
    20010518 cw     19:03      2.4      2.2     2.0     70

The difference between the latest model and the previous one is shown below :

The F3 spikes at azimuths 219.88 & 288.08 were removed by interpolation before the model was installed.

• The formal differences in (F1,F2,F3) are described by the rms scatters of (0.46", 0.41", 0.46") cf (0.52", 0.47", 0.77") previously.

• Installation of the new track model occurred at 13:50 HST 20 May 2001 - although I later find that it was 'installed' in the old (/jcmt_sw/mtroot/....) tree.

• The symmetry remains at reasonably normal levels, although the general upward trend in the 'baseline' measure of RY-vs-TY is noteworthy - see the plot.

• The strain gauge data are also updated, and appear normal.